"A VALUE TRANSFER SYSTEM"

Abstract

A value transfer system for transferring value in transactions between electronic purses as electronic cash has a transaction failure recovery procedure whereby a pending log stores transaction messages after they are sent. On detection of an error an interface device (IFD) can issue a payment resume command to re-send the last transaction message and resume the transaction.

Full Text

A value transfer system for transferring value in transactions between electronic purses as electronic cash has a transaction failure recovery procedure whereby a pending log stores transaction messages after they are sent. On detection of an error an interface device (IFD) can issue a payment resume command to re-send the last transaction message and resume the transaction.

We Claim:
1. A value transfer system comprising:
a plurality of electronic purses;
a plurality of application carrier devices (ACD's) for carrying the electronic
purses;
a plurality of interface devices (IFD's) for coupling together pairs of ACD's to
allow value transfer transactions to take place between pairs of electronic purses,
wherein a transaction between a pair of electronic purses in ACD's coupled by an
IFD comprises an exchange of transaction messages in a sequence according to a
predetermined protocol, each transaction message being sent from one electronic
purse of a pair to the IFD and from the IFD to the other electronic purse of the
pair;
characterized in that each electronic purse includes:
storage means in the form of a pending log which holds details of the current or
latest transaction;
recovery means effective to cause the IFD to invoke a recovery procedure if the
predetermined sequence of transaction messages fails; and
means for sending the last transaction message of the other electronic purse of the
pair to the one electronic purse to resume the transaction.
2. The value transfer system as claimed in claim 1, wherein the said recovery means
comprises means for interrogating one electronic purse of the pair to derive from
its pending log the last transaction message which it sent and means for sending
that transaction message to the other electronic purse of the pair to resume the
transaction.
3. The value transfer system as claimed in claim 1, wherein the said recovery means
comprises means for interrogating the other electronic purse of the pair to derive
from its pending log the last transaction message which it sent, if the last
transaction message of the one electronic purse results in an error when sent, and
means for sending the last transaction message of the other electronic purse of the
pair to the one electronic purse to resume the transaction.
4. The value transfer system as claimed in claim 1, wherein the said recovery means
comprises means for interrogating both electronic purses of the pair to determine
from their pending logs which electronic purse had progressed further in the failed
transaction; means for interrogating the electronic purse which had progressed
further in the failed transaction to derive from its pending log the last transaction
message which it sent; and means for sending that transaction message to the
other electronic purse of the pair to resume the transaction.
5. The value transfer system as claimed in claim 1, wherein the IFD is effective to
invoke the recovery procedure automatically and immediately during a
transaction on detection of a failure in the predetermined sequence of transaction
messages.
6. The value transfer system as claimed in claim 1, comprising means effective to
cause the IFD to interrogate the electronic purses at the beginning of a proposed
transaction to determine where there is a failed transaction pending between those
purses which may be capable of resumption so that a delayed recovery procedure
may be initiated.
7. The value transfer system as claimed in claim 1, wherein each electronic purse
has an exception log which is a store of the details of failed transactions, the
contents of the pending log being copied to a record in the exception log on
failure to recover a failed transaction.
8. A value transfer system such as herein described with reference to the
accompanying drawings.